cowboy vs cowpuncher

cowboy and cowpuncher both are nouns.

Word	Noun	Adjective	Verb	Adverb
cowboy	Yes	No	No	No
cowpuncher	Yes	No	No	No

As nouns, cowpuncher is a hypernym of cowboy; that is, cowpuncher is a word with a broader meaning than cowboy:

cowboy: a male hired hand who tends cattle and performs other duties on horseback
cowpuncher: a hired hand who tends cattle and performs other duties on horseback

Other hypernyms of cowboy include cowhand, cowherd, cowpoke, puncher, adult male, man.

cowboy (noun)	cowpuncher (noun)
someone who is reckless or irresponsible (especially in driving vehicles)	a hired hand who tends cattle and performs other duties on horseback
a performer who gives exhibitions of riding and roping and bulldogging
a male hired hand who tends cattle and performs other duties on horseback